Abstract: Two predicted peptide genes in Arabidopsis thaliana L., Peptide5 and Peptide6, was confirmed by RT-PCR in mRNA level. The expression profile indicated that both genes were generally expressed at different developmental stages and tissues as constitutive gene expression, and they also responded to six treatments including NaCl, PEG, MeJA (methyl jasmonate), SA (salicylic acid), cold and wound in transcription level. Analysis of the promoter sequence suggests that Pep-tide5 in Arabidopsis may contribute to the secondary xylem formation.